The invention relates to a battery cell which comprises at least one electrode unit having an anode, a cathode and a separator which is arranged between the anode and the cathode. The invention also relates to a method for controlling ion flow within the battery cell.
Electrical energy can be stored by means of batteries. Batteries convert chemical reaction energy into electrical energy. A distinction is drawn between primary batteries and secondary batteries in this case. Primary batteries are functional only once, whereas secondary batteries, which are also called accumulators, are rechargeable. In this case, a battery comprises one or more battery cells.
In particular, so-called lithium-ion battery cells are used in an accumulator. The said lithium-ion battery cells are distinguished, amongst other things, by high energy densities, thermal stability and extremely low self-discharge. Lithium-ion battery cells are used, amongst other things, in motor vehicles, in particular in electric vehicles (EV), hybrid vehicles (Hybrid Electric Vehicles, HEV) and plug-in hybrid vehicles (Plug-in Hybrid Electric Vehicles, PHEV).
Lithium-ion battery cells have a positive electrode, which is also called the cathode, and a negative electrode, which is also called the anode. The cathode and the anode each comprise a current collector to which an active material is applied. The active material for the cathode is, for example, a metal oxide. The active material for the anode is, for example, graphite or silicon.
Lithium atoms are stored in the active material of the anode. During operation of the battery cell, that is to say during a discharging process, electrons in an outer electrical circuit flow from the anode to the cathode. During a discharging process, lithium ions migrate from the anode to the cathode within the battery cell. In the process, the lithium ions are extracted from the active material of the anode in a reversible manner, this also being called deintercalation. During a charging process of the battery cell, the lithium ions migrate from the cathode to the anode. In the process, the lithium ions are again inserted into the active material of the anode in a reversible manner, this also being called intercalation.
The electrodes of the battery cell are of foil-like design and, with the interposition of a separator which separates the anode from the cathode, are wound to form an electrode winding. An electrode winding of this kind is also called a jelly roll. The two electrodes of the electrode winding are electrically connected to poles of the battery cell, which are also called terminals, by means of collectors. A battery cell generally comprises one or more electrode units. The electrodes and the separator are surrounded by a generally liquid electrolyte. The electrolyte is conductive to the lithium ions and allows the lithium ions to be transported between the electrodes.
In the event of a fault, for example in the case of a short circuit or overcharging, there may be a temperature increase in the battery cells. Destruction of the electrolytes and shrinkage of the separator may occur at a sufficiently high temperature. This may consequently lead to destruction of the battery cell, possibly in the form of an explosion.
A battery cell of this generic type is disclosed in DE 10 2012 217 451 A1. The battery cell has a cell housing which is produced, for example, from a metal. The cell housing is of prismatic, in particular cuboidal, configuration and is of pressure-resistant design. The battery cell comprises a diaphragm which deforms in the event of an overpressure within the cell housing and in the process triggers a short circuit.
U.S. 2013/0017432 A1 discloses a separator for battery cells. In this case, the separator is of multilayer construction, wherein individual layers have patterns with openings which are arranged in an offset, in particular complementary, manner in relation to one another.
U.S. 2005/0208383 A1 discloses a separator which has a porous base material on one side of which or on both sides of which a resin structure is provided.